1. Technical Field
Aspects of the invention relate to a sheet feeder capable of separating sheets one-by-one from a stack of the sheets in a holder by a sheet feed roller and a separation member having elasticity.
2. Related Art
Image recording apparatuses such as a printer, a copier, a facsimile machine, generally include a sheet feeder that separates cut sheets (recording sheets) one-by-one and feeds them to an image recording unit.
In Japanese Laid-Open Patent Publication No. 2002-173240, cut sheets are accommodated substantially horizontally in an open-top box shaped cassette body, inclined separation face plates are provided at established intervals in a sheet width direction and on a downstream side of the cassette body with respect to a sheet feeding direction, and a sheet feed roller is provided in an upper portion of the cassette body and rotates while pressing a surface of an uppermost sheet of the stack. The sheets are separated one-by-one from the stack by the sheet feed roller in cooperation with the inclined separation faceplates, and fed via a U-turn path (a U-shaped conveying path) toward an image recording unit disposed in the upper portion of the cassette body.
Japanese Laid-Open Patent Publication No. 2004-149297 discloses a sheet feeder having an inclined wall designed to place a stack of sheets diagonally downward, a bottom plate provided in a lower portion of the inclined wall and having an obtuse angle with respect to the inclined wall and extending in a sheet width direction, and a sheet feed roller that feeds an uppermost sheet of a stack held between the bottom plate and the inclined wall by pressing against the sheet. The bottom plate is provided with a sheet separating portion made of a stainless steel. The sheet separating portion is comprised of protrusions that are arranged at established intervals in a sheet feeding direction, arm portions that support the protrusions at both sides, and a base portion that supports the arm portions continuously. The protrusions are set to protrude by a specific amount from long holes formed along the sheet feeding direction in a metal holder fixed to the bottom plate. When an uppermost sheet is pressed and fed by the sheet feed roller, the uppermost sheet presses the protrusions at its lower edge, the protrusions move down from the long holes of the holder due to the deformation of the arm portions by elasticity. However, sheets except for the uppermost sheet are held down by the protrusions protruding from the long holes and thus the uppermost sheet only is separated and fed.
However, in the structure disclosed in Japanese Laid-Open Patent Publication No. 2002-173240, a large gap exists between a position where the inclined separation face plate is provided and a position where the inclined separation face plate is not provided, and a sheet being fed is likely to be creased at its end portion. On the other hand, if the sheet separating portion formed of metal sheet disclosed in Japanese Laid-Open Patent Publication No. 2004-149297 is provided at the inclined separation face plates located on the downstream side of the cassette body disclosed in Japanese Laid-Open Patent Publication No. 2002-173240, the holder may be deformed due to a pressing force generated when the sheet is fed by the sheet feed roller, the protrusions may greatly protrude from the long holes in the holder, the sheet may be strongly rubbed by the protrusions and a surface of the sheet may be easily damaged.
Especially when glossy paper, suitable for photo image recording, is fed from a stack of a few glossy papers held in a deep cassette capable of holding a number of sheets toward a U-turn path having small radius of curvature, the glossy paper may be strongly rubbed by the protrusions because the paper is inherently hard to bend and returns to its flat state. As a result, a surface (recorded surface) of the glossy paper may be easily damaged. Furthermore, if the protrusions are shaped in the form of a claw, scratches on the surface of the sheet may appear and be deep.